div.overflow_1 {
    width: 300px;
    height: 100px;
    border: 1px solid chocolate;
    overflow: hidden;
}

div.overflow_2 {
    width: 100px;
    height: 100px;
    font-size: 250%;
    border: 1px solid goldenrod;
    overflow: auto;
}

.box {
    width: 400px;
    height: 50px;
    border: 3px solid hotpink;
    margin-top: 10px;
    background-color: azure;
}

.pos_static {
    position: static;
    background-color: blueviolet;
}

.pos_relative {
    position: relative;
    right: -50px;
    /*有正有负*/
    top: 20px;
    background-color: blue;
    z-index: -100;
    /*使用z轴，有正有负*/
}

.pos_fixed {
    position: fixed;
    top: 0px;
    right: 0px;
    background-color: aqua;
}

.pos_absolute {
    position: absolute;
    top: 100px;
    left: 200px;
    background-color: cadetblue;
}

.menu:hover+.absolute_menu {
    display: block;
}

.absolute_menu {
    display: none;
    position: absolute;
    background-color: brown;
    top: 56px;
    left: 0px;
}

.pos_sticky {
    position: sticky;
    position: -webkit-sticky;
    /*官方定义*/
    background-color: blueviolet;
    top: 0;
    margin-left: 500px;
    z-index: 100;
}

.box_float {
    background-color: red;
    float: left;
}

.clf {
    clear: both;
}

li {
    float: left;
    width: 100px;
    border: 1px solid blue;
}